Were you aware that USDA is sponsoring research at the University of Connecticut to develop sterile varieties of Winged Burning Bush (Euonymus alatus) and Japanese barberry (Berberis thunbergii) — both non-native plants spreading aggressively into natural and agricultural areas in many parts of the USA.
Sounds like a good idea, right? After all, if the plant is sterile – in other words, it doesn’t produce viable seeds or berries – it can be safely planted without risk of its seeds being spread by birds (or wind) into other areas.
But history shows that this theory hasn’t worked well for other ornamental invasives. Sterile cultivars of the invasive purple loosestrife such as ‘Dropmore Purple’ and ‘Morden’s Pink‘ were found to eventually produce viable pollen and seed and happily cross-pollinate with the wild species.
Reversion from “sterile” to “fertile” has also been reported in a number of other plants marketed as “sterile”, including Bradford/Callery Pear (Pyrus calleryana), reported invasive from the Great Lakes south to the Gulf Coast. To quote from Jurassic Park, “Nature will find a way”.
The environmental problems caused by invasive plants spreading from home landscapes is well-known, at least by governmental agencies and ecologists, if not consumers. Both burning bush and barberry have significant negative impacts on natural systems when they grow where they don’t belong.
Although now banned for sale in many states, including Massachusetts and New Hampshire, introducing sterile cultivars are not the solution. The runaway horse left the barn years ago, and our unmanaged woodlands are now heavily infested.
Where barberry has taken over woodland areas, studies show the plant can alter the soil chemistry (pH) and increase nitrate levels, making the soil inhospitable to existing woodland trees and understory plants* who eventually decline along with the associated wildlife that depend on them.
The presence of barberry is also being linked with high numbers of Lyme Disease, a horrible disease now approaching epidemic levels in the northeast. Barberry’s thorny foliage is good cover for mice and small rodents, who researchers from the Cary Institute for Ecosystem Studies believe are the top apex of the Lyme Disease pathogen, more so even than deer.
So why do we want to continue the heavy reliance on these plants in the nursery trade? Why invest all the energy and tax dollars into development of plants that shouldn’t be growing here in the first place? Simply put, it’s about money.
Burning bush sales are said to top $38 million nationwide, and plant breeders will tell you that consumers want this plant, that they ask for it, and the work fulfills a real demand. I understand that a lot of people buy plants on impulse because of their color, or they see a plant in a friend’s yard and decide to buy it for their own property without researching it first.
But I’m willing to bet that most consumers are willing to take this advice: “Barberry is a bad choice for the environment. Plant THIS instead.” In my own experience as a garden coach, I have only had one client in 5 years that did not remove their burning bushes after I explained their impact on our natural ecosystems.
I feel quite proud that my advice has led to the removal of a couple of dozen winged burning bush from suburban Massachusetts yards. I believe that landscaping professionals have great power to influence landscaping trends, and we have a responsibility to educate consumers about the consequences of their landscaping choices.
Not all states consider invasive plants as a legislative priority at the moment, but local landscaping and nursery organizations seem to be picking up the slack. The CT Landscape & Nursery Association has implemented a voluntary phase-out of the use of invasive Japanese barberry cultivars (but unfortunately not burning bush), and hopefully other green industry organizations will follow suit.
It also appears that our federal agencies need to re-evaluate where they are devoting their energy. The USDA web site proudly announces that sterile barberry cultivars should be available for sale within a decade. OK, but in the meantime, our remaining intact natural support systems are increasingly degraded by the continuing presence of invasives in home and public landscapes.
We need to persuade our governmental agencies to re-allocate resources to cultivating and restoring native plant populations in our natural areas, not pandering to landscaping trends.
So, for gardeners looking for alternatives to winged burning bush and invasive barberry, what can they plant that offers the same outstanding characteristics without damaging the environment?
There is a native Euonymus atropurpureus (Eastern Wahoo) that has the blazing red color of the invasive variety. Other eastern native shrubs with fiery fall foliage are Virginia Sweetspire (Itea virginica) and Highbush Blueberry (Vaccinium corymbosum).
For the red/burgundy or gold foliage cherished in the Japanese barberry cultivars, try dark or gold-leafed cultivars of Ninebark (Physocarpus opulifolius) – pictured below.
If you’re looking for a low thorny hedging plant as living ‘barbed wire’ to keep unwanted visitors out, try the native Virginia or Carolina Rose (Rosa virginiana or carolina).
For lots more information about native alternatives to invasive plants, read through the NPWG series of articles titled Plant This, Not That:
Plant This, Not That (Connecticut)
Plant This, Not That (New York)
Plant This, Not That (New Jersey)
Plant This, Not That: Native Groundcovers (Maryland)
Plant This, Not That: Native Groundcovers (North Carolina)
Plant This, Not That Creeping Bellflower (Midwest)
Plant This, Not That (California)
* Studies cited:
Changes in Soil Functions Following Invasions of Exotic Understory Plants in Deciduous Forests (Department of Ecology, Evolution, and Natural Resources, Rutgers University, New Brunswick, New Jersey 08901 USA)
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